Mobcast has released a game adaptation of the 1996 movie Swallowtail Butterfly. Titled Swallowtail: Yami no Oogon Densetsu, the cellphone-based RPG can be downloaded by users of NTT DoCoMo's FOMA900i and 901i series cellphones. The game was planned and directed by Shin Megami Tensei mastermind Kouji Okada.

Swallowtail Butterfly was a controversial, yet popular movie directed by Shunji Iwai. Just like the movie, the game will take place in the fictional city of Yen Town. Players will have to earn money while travelling together with fellow party members including detectives, burglars and part-timers. Items that the player picks up in the automatically generated dungeons, can later be combined.

Swallowtail: Yami no Oogon Densetsu is available for a monthly usage fee of 300 yen ($2.54 US).